Anatomy of the CMC Joint

(See also: CMC arthritis)

Discussion

• base of thumb metacarpal articulates w/ saddle shaped trapezium;
• saddle shaped articulation provides inherent stability;
• radial lateral ligament, which is covered by APL tendon, inserts into the thumb metacarpal;

deep anterior oblique ligament (palmar beak ligament)

• originates on the tuberosity of the trapezium & insertes on ulnar and volar edge of metacarpal base;
• anterior oblique ligament provides mobility but prevents dislocation;
• ligament maintains volar stability of saddle joint;
• anchors volar lip of first metacarpal to trapezium and second metacarpal;
• maximum tension occurs in this ligament with the metacarpal in flexion, abduction, and supination;
• traditionally, it is thought that insufficiency of this ligament leads to basal joint arthritis;
• ligament may help function as a pivot for the first metacarpal during palmar abduction to allow pronation;

dorsal radial capsular ligament

• is covered by EPB & EPL;
• some consider this ligament to be more important than the volar ligament;
• sectioning of this ligament produces dorsoradial subluxation of the thumb metacarpal;

ulnar ligament;

• limits range of abduction & extension of thumb
• if this ligament is torn unopposed pull of APL & EPL & EPB muscles dislocates metacarpal shaft radially and proximally

• Functional anatomy of the carpometacarpal joint of the thumb.
• Osteoligamentous guidance of the movements of the human thumb.
• Ligamentous stability of the base of the thumb.
• An anatomic study of the stabilizing ligaments of the trapezium and trapeziometacarpal joint.